Project description:Disturbance events are an important component of the ecology of coral reefs and increasingly frequent disturbances coupled with a lack of population resilience may contribute to changes in the structure of coral reef communities. The harvest of the Caribbean octocoral Antillogorgia elisabethae provides an opportunity to explore the relationship between adult abundance and recruitment and the manner in which recruitment contributes to the resilience of local populations. Recruitment of A. elisabethae was monitored in 20, 1-m(2) quadrats at 8 sites along the southern edge of the Little Bahama Bank from 2004 through 2007. A. elisabethae has been harvested in The Bahamas for over fifteen years and all of the sites had been harvested three times, including a harvest during the course of the study. Abundances of adult colonies at those sites as well as a location that had not been harvested were also determined. Recruitment was highly variable, differing between sites, transects within sites, and, depending on the site, between years. Recruitment was best correlated with adult abundance averaged across the surrounding site. Regression analyses suggest abundance on smaller scales had only small effects on recruitment. The effects of the harvesting were site specific ranging from a 38 to 67% reduction in the density of mature colonies. The sites with the most abundant A. elisabethae continued to have the highest abundances after harvesting and there was no significant difference in recruitment before and after harvesting. Population size-structure at 6 of 8 sites that have been harvested multiple times exhibited an overall depletion in small colonies suggesting long term suppression of recruitment and declining populations. Severe depression of adult abundances coupled with local recruitment can create a negative feedback and lead to the decline of local populations. Populations that are dependent on self-recruitment are not resilient to large disturbance events.

Project description:BackgroundWhat are the determinant factors of community assemblies in the most diverse ecosystem in the ocean? Coral reefs can be divided in continental (i.e., reefs that develop on the continental shelf, including siliciclastic reefs) and oceanic (i.e., far off the continental shelf, usually on volcanic substratum); whether or not these habitat differences impose community-wide ecological divergence or species exclusion/coexistence with evolutionary consequences, is unknown.MethodsStudying Caribbean octocorals as model system, we determined the phylogenetic community structure in a coral reef community, making emphasis on species coexistence evidenced on trait evolution and environmental feedbacks. Forty-nine species represented in five families constituted the species pool from which a phylogenetic tree was reconstructed using mtDNA. We included data from 11 localities in the Western Caribbean (Colombia) including most reef types. To test diversity-environment and phenotype-environment relationships, phylogenetic community structure and trait evolution we carried out comparative analyses implementing ecological and evolutionary approaches.ResultsPhylogenetic inferences suggest clustering of oceanic reefs (e.g., atolls) contrasting with phylogenetic overdispersion of continental reefs (e.g., reefs banks). Additionally, atolls and barrier reefs had the highest species diversity (Shannon index) whereas phylogenetic diversity was higher in reef banks. The discriminant component analysis supported this differentiation between oceanic and continental reefs, where continental octocoral species tend to have greater calyx apertures, thicker branches, prominent calyces and azooxanthellate species. This analysis also indicated a clear separation between the slope and the remaining habitats, caused by the presence or absence of Symbiodinium. K statistic analysis showed that this trait is conserved as well as the branch shape.DiscussionThere was strong octocoral community structure with opposite diversity and composition patterns between oceanic and continental reefs. Even habitats with similar depths and overall environmental conditions did not share similar communities between oceanic and continental reefs. This indicates a strong regional influence over the local communities, probably due to water transparency differences between major reef types, i.e., oceanic vs. continental shelf-neritic. This was supported by contrasting patterns found in morphology, composition and evolutionary history of the species between atolls and reef banks.

Project description:Benthic organisms sustain coral reefs through their growth and metabolism, but less is known about how their released metabolites influence reef seawater microorganisms. To investigate metabolite composition of benthic exudates and their ecological significance for reef microbial communities, we harvested exudates from six species of Caribbean benthic organisms including stony corals, octocorals, and an invasive encrusting algae, and subjected these exudates to untargeted and targeted metabolomics approaches using liquid chromatography-mass spectrometry. Incubations with reef seawater microorganisms were conducted to monitor changes in microbial community composition using 16S rRNA gene sequencing and abundance in relation to exudate source and three specific metabolites. Exudates tended to be enriched in amino acids, nucleosides, and vitamins, indicating that benthic organisms contribute labile organic matter to reefs. The phytohormone indole-3-acetic acid was detected in octocoral exudates, suggesting that this metabolite facilitates microbial interactions within and outside of benthic organisms. Exudate compositions were species-specific and significantly enriched in the indole class of metabolites. Microbial abundances and specific microbial taxa responded differently in relation to exudates from stony corals and octocorals, demonstrating the link between benthic organismal composition, metabolite exudates, and microbial growth. Conversely, microbial communities did not respond to additions of the individual metabolites, suggesting that reef microorganisms likely provide diverse metabolite pools that support microbial growth. This work identifies, quantifies, and compares metabolites released from common Caribbean benthic organisms and indicates that recent shifts in benthic composition from stony to octocorals alter exudate composition and likely impact microbial community composition and function on coral reefs. UPLC-MS Metabolite uptake incubation assay is reported in the current study MTBLS3286UPLC-MS Metabolite collection incubation assays are reported in <a href='https://www.ebi.ac.uk/metabolights/editor/study/MTBLS2855' rel='noopener noreferrer' target='_blank'>MTBLS2855</a>

Project description:Benthic organisms sustain coral reefs through their growth and metabolism, but less is known about how their released metabolites influence reef seawater microorganisms. To investigate metabolite composition of benthic exudates and their ecological significance for reef microbial communities, we harvested exudates from six species of Caribbean benthic organisms including stony corals, octocorals, and an invasive encrusting algae, and subjected these exudates to untargeted and targeted metabolomics approaches using liquid chromatography-mass spectrometry. Incubations with reef seawater microorganisms were conducted to monitor changes in microbial community composition using 16S rRNA gene sequencing and abundance in relation to exudate source and three specific metabolites. Exudates tended to be enriched in amino acids, nucleosides, and vitamins, indicating that benthic organisms contribute labile organic matter to reefs. The phytohormone indole-3-acetic acid was detected in octocoral exudates, suggesting that this metabolite facilitates microbial interactions within and outside of benthic organisms. Exudate compositions were species-specific and significantly enriched in the indole class of metabolites. Microbial abundances and specific microbial taxa responded differently in relation to exudates from stony corals and octocorals, demonstrating the link between benthic organismal composition, metabolite exudates, and microbial growth. Conversely, microbial communities did not respond to additions of the individual metabolites, suggesting that reef microorganisms likely provide diverse metabolite pools that support microbial growth. This work provides novel information about the metabolites released from common Caribbean benthic organisms and indicates that the recent shifts in benthic composition from stony to octocorals alter exudate composition and likely impact microbial community composition and function on coral reefs. UPLC-MS Metabolite collection incubation assays are reported in the current study MTBLS2855UPLC-MS Metabolite uptake incubation assay is reported in <a href='https://www.ebi.ac.uk/metabolights/editor/study/MTBLS3286' rel='noopener noreferrer' target='_blank'>MTBLS3286</a>

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Caribbean octocoral metatranscriptomics

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